Sealed furnaces for the countergravity casting of metal are known, but typically have a limited molten metal capacity based on practical size. As a result, the casting process must be interrupted to recharge such furnaces with metal. Interrupting the casting process results in lost production and oft times results in scrap castings as a result of temperature losses in the equipment and the melt. Moreover, the introduction of large volumes of new metal into such furnaces often results in the introduction of contaminants into the metal which adversely affects the casting process and the castings made therefrom. Decontamination of the melt during recharging adds both cost and time to the process. Finally, considerable energy is lost in the frequent open transfer of molten metal into the furnace which not only wastes such energy but adds to the cost of the process.